The present invention relates to methods for water purification processing and the economic utilization of waste waters produced from water purification processing.
The disposal of saline water has become an expensive problem for society. For example, approximately 1.61 billion gallons of water containing approximately 800,000 tons of mixed sodium, calcium, magnesium chlorides and sulfates is produced from water treatment operations and oil fields in the state of California alone. This saline water must be disposed of, costing the state of California millions of dollars each year. Meanwhile the United States Geological survey recently determined that New Mexico has an astounding 15 billion acre feet of brackish ground water, and a single basin in West Texas alone was found to have 760 million acre feet of brackish ground water.
Many coal beds are located where traditional mining is not feasible. Instead, the coal beds are stripped of their associated methane which requires pumping water from the coal bed strata Methane migrates to gas wells where it is pumped out and transported for public use. The removed water is typically 900 to 1500 parts per million (ppm) of total dissolved salts (TDS). Unfortunately, the water is typically high in sodium and carbonate and/or bicarbonate.
Meanwhile, the disposal of saline water has become even more problematic in other parts of the world. As a result, billions of dollars are spent each year toward efforts to dispose of saline waters. Accordingly, it would be highly advantageous to provide improved methods of disposing of salty waters. It would even be more advantageous to provide methods of utilizing salty waters which provide a benefit to society, instead of simply disposing of the unwanted waters.
Water purification typically produces a first effluent of relatively “clean water” and a second effluent of “waste water” which includes unwanted contaminates. For purposes herein, clean water is defined to mean water including mean less than 0.05% by weight of the salts of Na, K, Ca, Mg, Fe, Cl, SO4, or CO3 or combinations thereof. Waste water is defined herein to mean water including more than 0.15% by weight of the salts of Na, K, Ca, Mg, Fe, Cl, SO4, or CO3 or combinations thereof. In addition to waste water, there is a substantial amount of “moderately saline water” around the world that has less saline than waste water but which is not generally accepted for irrigation or animal consumption. Thus, this moderately saline water is severely limited for its application and usefulness. As defined herein, “moderately saline water” means water that has 0.05% or more by weight and less than 1.00% by weight of the salts of Na, K, Ca, Mg, Fe, Cl, SO4, or CO3 or combinations thereof.
Known water purification processes proceed by numerous methods including ion-exchange, membrane softening, electrolysis, evaporation and precipitation. The softening of hard water take place by removing calcium and magnesium which is required for both industrial and household use. Known water softening processes proceed either by way of ion-exchange, membrane softening or precipitation. In the ion-exchange processes, the calcium (Ca2+) and magnesium (Mg2+) ions are exchanged for sodium (Na+) and the regeneration of the ion-exchange media is achieved with a large excess of NaCl. This processes creates a regeneration effluent being a relatively concentrated aqueous solution of sodium, calcium and magnesium chlorides which has to be discarded. Consequently, by this method, considerable amounts of sodium, calcium and magnesium salts in solution must be disposed of.
Alternatively, it is possible to soften water by using weak acid resins which exchange hydrogen (H+) for calcium (Ca2+) and magnesium (Mg2+), and to regenerate the spent resins with a mineral acid. While this method creates less saline water, it is more expensive and yields relatively acidic soft water which is corrosive. Meanwhile, membrane softening concentrates the calcium, magnesium salts and salts of other divalent ions to produce saline waters which require costly disposal.
The precipitation process has traditionally been carried out by the “lime soda” process in which lime is added to hard water to convert water soluble calcium bicarbonate into water insoluble calcium carbonate. This process also results in waste water which is difficult to filter and requires cumbersome treatment.
My previously issued patent, U.S. Pat. No. 5,300,123 relates to the purification of impure solid salts. Even this process produces salty waste water which must be disposed of. My latter issued patents U.S. Pat. Nos. 6,071,411; 6,374,539 and 6,651,383 relate to the processing and utilization of processed waste waters.
These processes preferably employ ion-exchange, preferably using soluble salts of sodium or calcium, to alter the salt content of treated water. Moreover, the resulting salts, clean effluents and waste water effluents are useful for various applications including for the treatment of soils for improving dust control, soil stabilization, adjusting the soil's sodium adsorption ratio (SAR), and treating root rot.
Unfortunately, even with all of the various water treatment processes of the prior art, there are billions of gallons of moderately saline water that are discarded or not utilized because it is far to expensive to purify such waters using known water treatment processes. This overabundance of salty water is troubling because there is an overwhelming world-wide need for water, particularly for human and livestock consumption. A recent report from the United Nations states that more than 50 percent of the nations in the world will face water stress or water shortages by the year 2025. By 2050, as much as 75 percent of the worlds's population could face water scarcity.
Even more troubling, in impoverished countries, humans and animals often suffer from calcium and magnesium deficiencies even though there may be millions of gallons of nearby saline waters. These saline waters typically contain some calcium and magnesium but contain too much sodium to be drinkable. Unfortunately, due to the expense and unavailability of equipment, this water cannot be processed for human or animal consumption.
Milk is recommended to provide an adequate diet of calcium and magnesium but milk is typically not affordable or available in sufficient quantities to meet the needs of children in developing countries or even the needs of children in poor areas of developed countries. Thus, there would be an incredible development if the saline water could be treated to lower the sodium but increase or maintain the calcium and magnesium to levels suitable for human and livestock consumption.
Water is also in great demand for soil treatment, particularly for irrigation. Unfortunately, moderately saline waters often have saline content which is not suitable for nearby irrigation. Thus, it would be extraordinarily advantageous if an inexpensive process were developed for processing moderately saline waters to produce an effluent suitable for irrigation.
Wind erosion of soil is also significant problem throughout the world. Due to small particle size and poor cohesion, finely divided soil is sensitive to the influence of wind. Such finely divided soil is found in agricultural lands, dunes, lake beds, construction sites and roads under construction. Erosion by wind causes the drifting of masses of soil in the form of dust. The erosion by wind causes the inconvenience of dust formation and the loss of valuable matter such as seed, fertilizer and plantlets. Dust storms are a danger to traffic and a health risk to persons located in the vicinity.
Moreover, the effects of wind erosion on soil can be enhanced by the influence of the sun and rain. The sun causes the evaporization of moisture from soil thereby reducing the cohesion of finely divided soil. Erosion of the soil by rain is caused by rain washing away soil. This is a particular problem when agricultural soil is washed away, damaging plant life and making the soil unusable for agricultural purposes. Further, due to the influence of erosion by rain, the unprotected slopes of ditches, channels, dunes and roads may collapse or be washed away.
Therefore, it is extremely important to prevent the effects of the sun, wind and water in eroding soil. As used herein, soil stabilization refers to the treatment of soils with chemicals to offset the tendencies of soils to be sensitive to small changes in the types of ions in the soil moisture as they effect the plasticity of the soil. For example, swelled clays, those with layers of “bound” water molecules, are more susceptible to movement under load. Soil stabilization of swelled clays can be effected by altering the types and/or amounts of ions in the soil mixture.
It has been proposed to prevent the shift, drift and erosion of soil by treating the surface layers of the soil with water dispersible high polymeric substances of a natural or synthetic nature. Examples of these high polymeric substances include starch ethers, hydrolyze polyacrylonitril, polyvinyl alcohol and carboxyrethyl cellulose. U.S. Pat. No. 3,077,054 discloses the use of polyvinyl acetate as an anti-erosion agent. U.S. Pat. No. 3,224,867 teaches the conditioning of soil with mono starch phosphate. U.S. Pat. No. 5,125,770 teaches treating the soil with a pre-gelatinized starch and a surfactant compound. Furthermore, it has been known to treat dirt roads with relatively pure solid sodium chloride (NaCl), calcium chloride (CaCl2), and mixtures of the two.
There are several drawbacks with the aforementioned soil treating compounds. The polymers mentioned have a relatively high price and have potentially harmful environmental properties. In addition, the starch ethers have proved sensitive to washing out by rain water. As a result, their effectiveness as an anti-erosion agent is severely limited.
An additional problem encountered throughout the world involves fungus. There are millions of acres of land in California, Arizona, New Mexico, Texas and the Sonora and Sinaloa areas of Mexico where crop production is almost impossible due to fungus which attack virtually all dicotyledonous plants of which there are more than 2,000 species. These include cotton, alfalfa and citrus trees. The lack of productivity is due to excessive calcium carbonate in the soil which minimizes swelling to the point that carbon dioxide from decaying humus concentrates to more than about 3.2% CO3, where fungus thrives. These fungus, primarily Phytomatotrichum omnivorim (Shear) Duggar, have three stages of development called the mycelium, conidium and scelerotia. The first stage, referred to as mycelium, involves the development of a fine filament which branches out throughout the soil and forms a tight web around plant roots. After the filament reaches the soil surface, a white mat forms on the surface, referred to as conidium. When mature, the mycelium develops multicellular bodies called scelerotia which can extend to a depth of up to twelve feet into the soil.
About 1970, it was discovered that the addition of sodium to soil offset the excess calcium in the soil. This increased the soil permeability and avoided the build-up of carbon dioxide that permits the root rot to flourish. Sodium chloride has been applied where the soil drains readily and the excess chloride and sodium are leached away by rainfall or irrigation. Meanwhile, sodium sulfate is preferable because 1) the sulfate supplies the nutrient sulfur, 2) the sulfate combines with calcium to form gypsum and gypsum soils typically do not support root rot, 3) gypsum buffers excess sodium assisting its leaching from the soil, and 4) there is no additional chloride residue which can leach into the water table. Unfortunately, sodium sulfate has always been too costly to be used to treat soil for farming. Recently, it has been suggested that solid mixtures of salts removed from water softening processes can be used to control root rot. However, salts removed from water softening are still relatively expensive and the process of utilizing salts recovered from waste water has not been adopted within the agricultural community.
Still an additional problem encountered in agriculture is that soil is often too high in sodium and/or too high in salinity. Farmland and irrigation water is often unacceptably high in sodium. Irrigation waters containing high amounts of sodium salts versus calcium and/or magnesium salts can create a buildup of sodium in the soil. This excess soil results in the dispersion of soil colloidal particles and an increase in soil pH. The dispersion of colloidal particles causes the soil to become hard and compact when dry and increasingly resistant to water infiltration and percolation. The sodium rich soil also becomes resistant to water penetration due to soil swelling when wet.
The total salinity of soil and irrigation water is also of concern. Salinity refers to the total salts within the water, with the significant positive ions (cations) in salinity being calcium, magnesium and sodium and the significant negative ions (anions) being chloride, sulfate and bicarbonate. All irrigation water contains some dissolved salts. When soil has a high content of dissolved salts, or the irrigation waters have sufficient salts to increase the salinity of the soil, the soil has the tendency to hold the water instead of releasing the water for absorption by plant roots by osmotic pressure. Even if the soil contains plenty of moisture, plants will wilt because they cannot absorb necessary water.
Ironically, though there is an overabundance of saline waters that are contaminated with the salts of Na, K, Ca, Mg, Fe, Cl, SO4, and CO3 that, as discussed above, is extraordinarily expensive to dispose of, millions of dollars are spent each year on salts such as sodium chloride for deicing highways. It would thus be advantageous if the salts in saline water could be used for deicing highways.
It would also be highly desirable to provide a method for treating soil that is of low cost and utilizes a material or compound which is readily available. It would be even more advantageous if salty waters could be processed to produce waters useful to treat soil to control dust and effect soil stabilization.
It would also be desirable to provide a method inhibiting root rot in soil.
Moreover, it would be desirable to provide a method of maintaining the proper salinity levels and salinity equilibrium in soil to enhance the agricultural properties of soil.
And of course, it would be most desirable to provide a method of processing waters, particularly those having high sodium content, to produce an effluent having a low sodium content but high magnesium and calcium content for human and animal consumption.
Finally, it would be desirable if all of the aforementioned objectives could be accomplished while overcoming the expensive and problematic concerns facing this country and the rest of the world, specifically, the disposing of saline waters. It would further be desirable if this objective could be obtained while simultaneously meeting the above described needs.